1, commonly used wires and cables according to the use of what kinds of points?
A: According to the use can be divided into bare wire, insulated wire, heat-resistant wire, shielded wire, power cables, control cables, communication cables, radio frequency cables and so on.
2, what kinds of insulated wires?
A: There are several kinds of insulated wires: PVC insulated wires, PVC insulated flexible wires, Nitrile PVC mixture insulated flexible wires, rubber insulated wires, agricultural underground buried aluminum core plastic insulated wires, rubber insulated cotton yarn textile flexible wires, PVC insulated nylon sheathed wires, PVC insulated flexible wires for power and lighting, and so on.
3, cable tray is suitable for what occasions?
A: Cable tray is suitable for general industrial and mining enterprises indoor and outdoor overhead laying of power cables, control cables, can also be used for telecommunications, radio and television departments in the indoor and outdoor erection.
4, what are the cable accessories?
A: Commonly used electrical accessories are cable terminal junction box, cable intermediate junction box, connecting pipe and terminals, steel wiring trough, cable tray and so on.
5, what is called cable intermediate joints?
A: Connecting the cable and cable conductor, insulation shield and protective layer, in order to connect the cable line device, called the cable intermediate joints.
6, what is called the main electrical wiring?
A: Electrical main wiring is a power plant, substation in the main electrical equipment and bus connection, including the main bus and plant power system according to certain functional requirements of the connection.
7, in the selection of power cable cross-section, which provisions should be followed?
A: The selection of power cables should comply with the following principles:
(1) The rated voltage of the cable should be greater than or equal to the rated voltage of the power supply system at the point of installation;
(2) The continuous allowable current of the cable should be equal to or greater than the maximum continuous current of the power supply load;
(3) Core cross-section to meet the requirements of the stability of the power supply system in the event of a short circuit;
(4) According to the length of the cable to check whether the voltage drop meets the requirements;
(5) The minimum short-circuit current at the end of the line should be able to make the protective device operate reliably.
8, cross-linked polyethylene cables and oil paper cables compared to what are the advantages?
A: (1) easy to install, because it allows a small minimum bending radius, and light weight;
(2) Not subject to line drop *;
(3) Good thermal performance, high permissible operating temperature and large transmission capacity;
(4) Simple cable accessories, all dry structure;
(5) Simple operation and maintenance, no oil leakage problem;
(6) Lower price;
(7) High reliability, low failure rate;
(8) fewer manufacturing processes, simple technology, significant economic benefits.
9, fixed AC single-core cable clamp has what requirements? Why?
A: The fixture should be free of iron to form a closed magnetic circuit, this is because when the cable core through the current, the magnetic lines of force generated around it, the magnetic lines of force and the size of the current through the core is directly proportional to the use of iron and other magnetically conductive materials, according to the electromagnetic induction can be seen in the iron will produce eddy currents in the cable heating, or even burned out of the cable. So do not use iron for single-core AC cable fixed fixture.
10,What are the biggest features and advantages of the following accessories for heat-shrinkable cable head?
A: The biggest feature of heat shrinkable accessories is to replace the traditional stress cone with stress tube, which not only simplifies the construction process, but also reduces the size of the terminal of the connector, easy to install, saves time and labor, has superior performance and saves metal. Heat-shrinkable cable accessories set of perfusion and dry pack type as a whole, a collection of the advantages of these two accessories.
11, cable laying should be carried out before what inspection work?
A: (1) The bracket should be complete, complete paint.
(2) cable type, voltage, specifications in line with the design.
(3) cable insulation is good, when in doubt about the sealing of the oil paper cable, moisture judgment should be carried out; direct buried cable and small bottom cable should be qualified by DC voltage test difficult; oil-filled cable oil samples should be tested qualified.
(4) oil-filled cable oil pressure should not be less than 1.47MPa.
12, the oil paper insulated power cable sealing doubt, how to use a simpler way to check whether the cable insulation paper moisture?
A: The cable insulating paper ignited or put into the 150 ℃ or so in the cable oil check, no “hiss” sound or white foam appears, that is not damp.
13, cable signage should indicate what content? What are the requirements for the preparation?
A: The signage should indicate the cable line design number, cable type, specifications and starting point, parallel use of the cable should be sequential number. Requirements for clear handwriting, not easy to fall off.
14, directly buried cable orientation signs should be set in which position?
A: At both ends of the cable, cable straight section of 50 ~ 100m at the cable joints several cable change direction of the corner.
15, the production of cable joints with yellow wax silk tape, black glass lacquer tape, non-alkali glass tape, etc., how to moisture treatment before construction?
A: (1) constant temperature drying method: the insulating tape rolled into a diameter of 25 ~ 30mm rolls, into the 110 ~ 120 ℃ constant temperature drying oven baked 4 ~ 5h, cooled and dried out, put into a dry sealing cylinder.
(2) oil-immersed moisture method: the insulating tape rolls into the constant temperature of 120 ~ 130 ℃ in the cable oil, from the bottom of the pot to maintain a distance of 30mm, after a certain period of time after the oil surface no longer produces bubbles removed, loaded into the barrel of the cable oil stored in the oil should be more than the level of all the loaded objects and will be sealed.
16, what is the role of the outer cable sheath?
A: to protect the inner sheath from mechanical damage and chemical corrosion, enhance mechanical strength.
17, outdoor cable trench should meet what requirements?
A: The upper part of the cable trench should be slightly higher than the ground, covered with a concrete cover, the cable should be laid flat in the bracket, there is a good drain.
18, what is the role of the inner cable protection layer?
A; so that the insulation will not be in contact with water, air or other objects, to prevent the insulation from moisture and insulation from mechanical damage.
19, the use of wire cutters should pay attention to what?
A: Before use, be sure to check whether the insulation of the insulation handle is intact, the use of wire cutters may not be used to cut more than the specifications allowed by the metal wire, and prohibit the use of wire cutters instead of hammers to hit the tool, so as not to damage.
20, what is called insulation strength?
A: Insulating material in the electric field, when the electric field strength increases to a certain limit will be broken, this leads to insulation breakdown of the electric field strength is called insulation strength.
21、What are the advantages of cross-linked heat shrinkable cable accessories?
A: This is a new type of material, it is now compared with other types of accessories with superior electrical performance, small size, small quality, easy to install, matching materials and other advantages, in addition to climate resistance, dirt resistance, flame retardant self-extinguishing ability.
22, what are the requirements for the mechanical strength of the cable conductor connection point?
A: The mechanical strength of the connection point, generally lower than the tensile strength of the cable conductor itself, for fixed laying of power cables, the tensile strength of the connection point is required to be not less than 60% of the tensile strength of the conductor itself.
23, power cable insulation materials should have what main properties?
A; should have the following main properties:
(1) high breakdown strength;
(2) low dielectric loss;
(3) fairly high insulation resistance;
(4) Excellent discharge resistance;
(5) A certain degree of flexibility and mechanical strength;
(6) insulation properties of long-term stability.
24, mechanical laying of cables, what are the provisions of traction strength?
A: For copper-core cables, when the traction head, the permissible traction strength of 70N/cm; for aluminum-core cables, when the traction head, the permissible traction strength of 40N/cm; if the use of steel wire mesh sheath traction, the permissible strength of lead-sheathed cables for 10N/cm;
Lead sheathed cable for 40N/cm.
25, what are the provisions of the cable protection pipe?
A: (1) When cables need to be laid through the protection pipe, the inner diameter of the pipe should not be less than 1.5 times the outer diameter of the cable, and the inner diameter of the concrete pipe, terra cotta pipe, asbestos, cement pipe should not be less than 100mm;
(2) The bending radius of the cable pipe shall be in accordance with the bending radius of the cable being threaded;
(3) Each pipe should not exceed a maximum of three elbows, and there should be no more than two right-angle bends.
26, how to measure the outer diameter of the cable sheath?
A: In the sheath of the circumference of the uniform distribution of five points, the measurement of the outer diameter of the sheath and its average, the average diameter of the outer diameter of the sheath for the outer diameter of the sheath.
27, different cross-section of the copper core cable how to connect?
A: different cross-section of the copper cable connection, can be used to open the weak back of the copper receiver to tin welding method of connection, can also be used pure copper rod according to different cross-section requirements connected to the copper receiver, crimping method of connection.
28, a brief description of the 10KV cross-linked cable heat-shrinkable production of indoor terminal head process?
Answer; (1) preparation stage: check whether the heat-shrinkable cable accessories are complete, whether the model is matched, check and confirm that the cable has no moisture after the cable.
(2) Remove the excess cable and decide the cable length according to the site conditions.
(3) Strip off the sheath.
(4) Weld the grounding wire, weld the grounding wire to the steel tape.
(5) Fill the trident port and wrap around the sealant.
(6) Install the three-core branch sheath, put the sheath into the root and shrink it from the middle, first to the root and then to the finger.
(7) Peel copper tape and outer semi-conductive layer, peel and cut three-core branch sheath mouth more than 20mm of copper tape, prohibit damage to the main insulation, remove clean semi-conductive layer.
(8) Installation of the stress tube, the mouth end of the partial branch sleeve butt after heat shrinkage.
(9) Installation of terminals.
(10) Installation of insulation pipe.
(11) Installation of sealing tube.
(12) Installation of phase color pipe after verification.
29, indoor and outdoor prefabricated terminal installation steps?
A: (1) the cable according to the predetermined position in place, fixed, clean the surface, with reference to the instructions to peel off the outer sheath, if any special needs, the outer sheath peeling length can be adjusted, respectively, by the copper tape, the outer sheath armored lead out of the 2 groups of ground.
(2) Measure the required size upward from the mouth of the outer sheath, cut off the excess cable, set into the heat-shrinkable three-finger sleeve to the root of the three-forked mouth by the middle of the heating contraction, and measure the required size upward from the upper mouth of the finger sleeve (350~380mm for 35kv). Remove excess copper tape (retained 20mm), and then retain the semiconductor predetermined position, crimp out terminals sealed.
30, wire and cable applications are mainly divided into three main categories :
(1), the power system
Power systems using wire and cable products are mainly overhead bare wire, busbar (bus), power cables (plastic cable, oil paper power cable (basically replaced by plastic power cables), rubber cables, overhead insulated cables), branch cables (to replace some of the busbar), electromagnetic wire, and electrical equipment for power equipment wire and cable, etc..
(2), information transmission system
Wire and cable for information transmission systems are mainly telephone cables, television cables, electronic cables, radio frequency cables, fiber optic cables, data cables, electromagnetic wires, power communication or other composite cables.
(3), mechanical equipment, instrumentation systems
This part in addition to overhead bare wire almost all other products are applied, but mainly power cables, electromagnetic lines, data cables, instrumentation cables and so on.
31, wire and cable products are mainly divided into five categories:
(1), bare wire and bare conductor products The main feature of this category of products is: pure conductor metal, no insulation and sheath layer, such as steel-core aluminum stranded wire, copper and aluminum busbar, electric locomotive line, etc.; processing technology is mainly pressure processing, such as smelting, calendering, pulling, stranding/tightening stranding, etc.; the product is mainly used in the outskirts of the city, the countryside, the user’s main line, switchgear, etc..
(2), the main features of this category of power cables are: extruded outside the conductor (winding) package insulation, such as overhead insulated cables, or a few core stranded (corresponding to the power system’s phase, zero and ground), such as more than two-core overhead insulated cables, or then increase the sheath layer, such as plastic / rubber-coated wires and cables. The main process technologies are pulling, stranding, insulation extrusion (winding and wrapping), cable formation, armoring, sheath extrusion, etc., and there are some differences in the combination of different processes for various products.
Products are mainly used in the generation, distribution, transmission, transformation, power supply lines in the transmission of strong electrical energy, through the current (tens of amps to thousands of amps), high voltage (220V to 500kV and above).
(3), electrical equipment with wire and cable the main features of this category of products are: a wide range of specifications, a wide range of applications, the use of voltage in 1kV and below more, in the face of special occasions continue to derive new products, such as fire-resistant cables, flame-retardant cables, low-smoke halogen-free / low-smoke low-halogen cables, anti-termite, anti-mouse wire and cable, oil/cold/temperature/abrasion-resistant cable, medical/agricultural/mining cables, thin-walled wires and so on.
(4), communication cables and optical fibers (brief introduction) With the last two decades, the rapid development of the communications industry, the product also has an amazing rate of development. From the simple telephone and telegraph cables in the past to the development of thousands of pairs of words cable, coaxial cable, fiber optic cables, data cables, and even a combination of communication cables.
The structure of this type of product size is usually small and uniform, manufacturing precision requirements.
(5), electromagnetic wire (winding wire) is mainly used for a variety of motors, instruments and meters.
Derivative/new products of wire and cable
Derivative/new products of wire and cable is mainly due to the application occasions, application requirements are different and the convenience of equipment and reduce equipment costs and other requirements, and the use of new materials, special materials, or change the product structure, or to improve the process requirements, or will be a combination of different varieties of products and produce.
The use of different materials such as flame retardant cables, low-smoke halogen-free/low-smoke low-halogen cables, anti-termite, anti-rat cables, oil/cold/temperature-resistant cables and so on;
Changing the product structure such as: fire-resistant cables, etc;
Improvement of process requirements such as: medical cables, etc;
Combining products e.g. OPGW etc;
Convenient installation and reduce equipment costs such as: prefabricated branch cables.
32, busbar device construction is complete, what checks should be carried out?
A: The following checks should be carried out:
(1) the processing of metal components, preparation, welding and screwing should be in accordance with the provisions;
(2) Each bolt, washers, cotter pins and other parts should be complete and reliable;
(3) Busbar preparation and mounting frame should be in accordance with the provisions of the phase and the electrical distance to ground in accordance with the requirements;
(4) Porcelain parts, iron parts and gluing should be complete, oil-filled casing should be free of oil seepage and normal oil level;
(5) The paint is complete, the phase color is correct, and the grounding is good.
33, in 35kv and the following power cable joints, to improve the electric field distribution of its sheath disconnections in several ways (please list five), and briefly describe its methods.
A: (1) Expansion flare: pry up the edge of the lead sheath at the lead sheath cut-off into a flared shape, and its edge should be smooth, rounded and symmetrical.
(2) Reserve tundish insulation: leave a section of tundish insulation paper between the lead package cut and the cable core separation point.
(3) Remove semi-conductive paper: Remove the semi-conductive paper below the flare.
(4) Wrap around the stress cone: with insulating wrapping tape and conductive metal materials wrapped into a cone, artificially expanding the shield to improve the electric field distribution.
(5) Equipotential method: For dry-wrapped or cross-linked polyethylene cable head, wrap a section of metal tape on the insulating surface of each core profile and connect them together.
(6) Installation of stress control tube: For 35kv and hair under the heat-shrinkable tube cable head, first of all, from the direction of the end of the core copper shielding layer through the semiconductor tape to the core insulation profile wrapped around 2 layers of semiconductor tape, and then the corresponding specifications of the folding stress tube, set in the end of the copper shielding at the end of the heat-shrinkable molding.
34, cable bracket processing should meet what requirements?
Answer:
(1) steel should be straight, no obvious distortion, undercutting error should be within 5mm, the cut should be no curled edge, burr;
(2) The bracket should be firmly welded, no obvious deformation, the vertical clearance between the horizontal supports and the design deviation should not be greater than 5mm;
(3) metal bracket must be anticorrosion treatment, located in hot and humid, salt, fog and chemical corrosion areas, should be based on the design of special anticorrosion treatment.
35、List the cable racks you are familiar with.
A: welding type E-type frame, assembly type E-type frame, bridge cable rack, cable tray, hook bracket, single cable bracket.
36, laying cables should meet what requirements?
A: The following requirements should be met:
(1) safe operation, as far as possible to avoid all kinds of external damage, improve the reliability of power supply of cable lines;
(2) economic aspects, from the aspect of the most economical investment;
(3) Construction aspect, the path of the cable line must be convenient for spinning work and maintenance after commissioning.
37, the production of cable terminal head or intermediate joints of the insulating materials are?
A: There are insulating rubber, insulating tape, insulating pipe, insulating gloves, insulating resin and so on.
38, a brief description of the general operating procedures for the production of cable head. A：(1)Preparation before making: including ○1 reading installation instructions; ○2 inspecting the site; ○3 preparing materials; ○4 cable moisture test; ○5 pre-production test, etc..
(2) The process of making joints: including ○1 cutting excess cable; ○2 stripping of cable protection layer; ○3 connecting conductors; ○4 wrapping insulation (or shrinking tubing); ○5 installing joint shells; ○6 filling insulant; ○7 performing sealing treatment, etc.
(3) Electrical testing after fabrication.
39, cable protection pipe processing should meet what requirements?
(1) the mouth of the pipe should be * sashay and sharp fluting, the mouth of the pipe should be made into a flared shape.
(2) cable pipe after bending, there should be no cracks and significant deflated phenomenon, the degree of bending flat should not be greater than 10% of the outer diameter of the tube; cable pipe bending radius should not be less than the minimum allowable bending radius of the cable penetration.
(3) metal pipe should be coated with anticorrosive paint or leaching table on the exterior, galvanized pipe zinc layer flaking should also be coated with anticorrosive paint.
40, the arrangement of cables in line with what requirements? A: (1) power cables and control cables should not be configured in the same layer of support.
(2) high and low voltage cables, strong and weak power control cables should be configured in layers according to the order of the general situation is appropriate from top to bottom, but in the case of high-voltage cables containing more than 35kv introduced into the cabinet disk, in order to meet the bending radius, can be configured from the bottom up.
41, cable trench cable laying method is what?
A: the method of laying cables in the cable trench and direct burial cable laying methods similar to the general pulley can be placed in the ditch, the application is complete, the cable will be placed on the bottom of the ditch or bracket, and cable labeling on the cable tied.
42, what are the common equipment for cable laying?
A: (1) air compressor, mainly used to destroy the road surface, in preparation for future cable laying;
(2) electric winches or cable traction machine, mainly used to drag the cable;
(3) cable conveyor, with the use of traction machine to overcome the huge friction, reduce the damage to the cable;
(4) Cable tray payoff bracket;
(5) Roller device.
(6) Anti-twist , reduce the twisting of wire rope;
(7) Cable tray braking device;
(8) Tension meter.
43, cable trench in the bracket installation distance requirements? A: cable fixed to the wall of the cable trench and tunnel, horizontal device, when the cable OD equal to or less than 50mm should be every 1m plus a support; OD greater than 50mm cable every 0.6m plus a support; rows of triangular single cable, every 1m should be strapped firmly, vertical device, every 1 ~ 1.5m to be fixed.
44, how to deal with power cables and control cables in the same bracket installation?
A: Power cables and control cables generally should not be laid in the same bracket, when the cable is less and control cables and power cables laid in the same bracket, should be separated by a partition.
45, how to install the cable tunnel grounding wire?
A: The full length of the tunnel and ditch should be installed continuous grounding line, grounding line should be connected to all the brackets, the two ends and grounding pole connected. The specification of the grounding wire should meet the design requirements. Cable lead package and armor in addition to insulation requirements, should be all interconnected and connected to the grounding wire, cable racks and grounding wires should be coated with antirust paint or galvanized.
46、What are the requirements for fire blocking of cable holes?
A: For larger cable through the hole, such as cable through the floor, etc., the use of fire plugging material blocking, should be based on the actual situation, the first cable surface coated with four to six layers of fireproofing paint, the length of the hole from the following 1.5m or so, and then processed into a fire-resistant material with a certain strength of the board tray fire plugging material to ensure that the blocking of solid and easy to replace the cable when the dismantling, blocking and sealing of dense non-porous in order to effectively block the smoke blocking fire.
47, the torch should pay attention to what checks before ignition?
A: The following checks should be carried out:
(1) whether the pump leakage or seepage of oil, oil drum and nozzle leakage of oil and gas;
(2) Whether the amount of oil in the oil drum is more than 3/4 of the drum’s capacity, and whether the screw plug for refueling is tightened.
48, the use of blowtorch should pay attention to what matters?
A: (1) The maximum oil injection volume of the blowtorch is 3/4 of the oil drum volume;
(2) start pumping pressure should not be too large, after ignition of the flame from yellow to blue can be used;
(3) There should be no flammable materials around, and the air should be circulated;
(4) Close the regulating switch when it is out of use, after the fire goes out, slowly loosen the oil hole cover to deflate, after the air is discharged, loosen the regulating switch, and then loosen the hole cover after it is completely cooled down;
(5) kerosene blowtorch and gasoline blowtorch to be used separately.
49、What is the use of manual hydraulic pliers? How to operate?
A: The connection of two wires is usually the two wire ends into the same material made of pressure tube, crimping pliers to squeeze several pits, so that the wires are connected together, crimping, the handle upward when the plunger moves outward, the lower chamber of the inlet valve produces a vacuum, the oil tank oil into the plunger chamber. When the handle is pressed down, the plunger moves inward, the oil is pressurized, so that the inlet valve is closed, open the outlet valve, so that the oil pressure into the hydraulic cylinder, pushing the piston and the yang die, yang, yin die is placed between the pressure tube, when the crimp is squeezed by the pit depth of a certain value, open the return valve, the piston automatically return, after a pit, move the pressure pliers, and then press the next one.
50, commonly used low-voltage power cables according to the different insulation and protective layers, can be divided into which categories?
A: (1) oil-impregnated paper insulation lead package (or aluminum package) power cables;
(2) non-drip oil-impregnated paper-insulated power cables;
(3) polyvinyl chloride insulation polyvinyl chloride sheathed power cables;
(4) Cross-linked polyvinyl chloride insulated polyethylene sheathed power cables;
(5) Cross-linked polyvinyl chloride insulated polyvinyl chloride sheathed power cables;
(6) rubber insulated power cables.
51, the categories of commonly used insulation materials? Give examples?
A: (1) inorganic insulating materials: mica, asbestos, marble, porcelain, glass and so on;
(2) organic insulating materials: resin, rubber, paper, hemp, cotton yarn, etc.;
(3) mixed insulating materials: with the above insulating materials processed and molded name kind of insulating materials.
52, in which case the use of pipe laying? What are the advantages?
A: Row pipe laying is generally used in and other buildings, highways or railroads cross the place, and sometimes also used in the building of dense areas. The main advantage is that it occupies less space, can withstand large loads, cables do not affect each other, more secure.
53, what is the long-term allowable capacity of the cable?
A: The cable long-term allowable current-carrying capacity refers to the cable through the specified current, after thermal stabilization, the cable conductor to reach the long-term allowable operating temperature of the current value.
54, what are the factors that determine the long-term allowable current-carrying capacity of the cable?
A: There are the following three factors determine:
(1) The long-term allowable operating temperature of the cable;
(2) The thermal performance of the cable itself;
(3) The cable device situation and the surrounding environment of the heat dissipation conditions.
55, there are several ways of laying cables?
A: There are several kinds:
(1) Buried directly in the ground;
(2) Installed in the cable trench;
(3) Installed in underground tunnels;
(4) Installed on walls or canopies inside buildings;
(5) Installed on a bridge;
(6) Laying in a discharge pipe;
(7) Laying under water.
56, how to carry out the cable pipe connection work?
A: cable pipe connection, must be connected with buckles and pipe joints, such as the use of welding, can not be directly welded, the connection should be set on a section of thick pipe and then welded, so as not to weld slag fall into the pipe.
57, the production of cable head, the upper and lower wrench bending cable core requirements?
A: When bending the core, shall not damage the paper insulation, the core bending radius shall not be less than 10 times the core of the cable. Production should be particularly careful, should make the core bending part of the uniform force, otherwise it is very easy to damage the insulation paper.
58, briefly describe the plastic cable heat shrinkage sealing method
A: The heat shrinkage method is applicable to the sealing of medium- and low-voltage rubber and plastic cable joints and terminal heads, and can also be applied to non-drip and viscous impregnated insulated cables. The use of cross-linked polyethylene-type and silicone rubber-type two major types of heat shrinkable tubing can be uniformly contracted when exposed to heat. This tube set in the predetermined adhesive sealing parts, and in the adhesive and parts coated with hot melt adhesive, when heated to a certain temperature, the heat shrinkable tube will shrink, while the hot melt adhesive melting, to be naturally cooled that is the formation of a good sealing sealing layer.
59, with electric pipe bender bending cable protection pipe should pay attention to what?
A: (1) The bender should be understood by the performance and familiar with the operation of knowledge of the personnel to operate;
(2) must be checked before use, buttons, operating handles, trip switches should be intact, the bender must be reliably grounded;
(3) Selection of molds that meet the requirements to determine the required bending radius;
(4) Around the construction site, there should be sufficient scope of activities;
(5) use to wait for the idle normal, before working with a load, running, it is strictly prohibited to use hands and feet to contact its rotating parts;
(6) The work should be completed in time to stop the power and release the oil pressure.
60, the content of the cable inventory and the meaning of the cable number?
A: The cable inventory is the basis for applying cable and guiding construction, operation and maintenance of the archives. Should be included in each cable number, starting point, model, specifications, length, and categorized statistics out of the total length, the control cable should also list the spare core of each cable.
Cable numbering is to identify the sign of the cable, so the requirements of the whole plant number is not repeated, and has a certain meaning and law, can express the characteristics of the cable.
61, cable laying methods currently used can be divided into several categories?
A: (1) artificial laying, that is, the use of human sea tactics, in one or more people to coordinate the command, according to the regulations for laying;
(2) Mechanized laying, that is, the use of rollers, tractor, conveyor, through a synchronous power supply for control, safer;
(3) a combination of manual and mechanical, some sites due to more turns, the construction is difficult, all with machinery is more difficult, so this method is used.
62, the control of the secondary circuit wiring should meet what requirements?
A: (1) according to the map construction wiring is correct;
(2) The electrical connection of the wire should be firm and reliable;
(3) The wires in the panel cabinet should not have joints, wire core should be free of damage;
(4) The end of the cable core should be marked with its circuit number, the number should be correct, clear writing and not easily decolorized;
(5) Wiring should be neat, clear, beautiful, wire insulation should be good, no damage;
(6) Each side of each terminal wiring should be one, not more than two.
63, what are the requirements for cable ducting?
Answer: (1) The distance from the top of the pipe to the ground in the plant is 0.2m, under the sidewalk is 0.5m, and the general area is 0.7m;
(2) In the change of direction and branch should be installed in the row of pipe well pit, the length of more than 30mm should also be added well pit;
(3) The depth of the well pit is not less than 0.8m, and the diameter of the manhole is not less than 0.7mm;
(4) Drainage pipe should be inclined to well pit 0.5% ~ 1% drainage slope.
64, for the cable conductor connection point resistance requirements?
A: Requirements for the connection point of the resistance is small and stable, the resistance of the connection point and the same length, the same cross-section of the conductor ratio, for the new installation of the terminal and intermediate head, should be no more than 1; for the operation of the terminal and intermediate head this ratio should not be greater than 1.2.
65, cable joints and intermediate head design should meet what requirements?
A: The requirements that should be met are:
(1) High compressive strength and good conductor connection;
(2) High mechanical strength and small medium loss;
(3) simple structure, strong sealing.
66, what is the cable fault? How many common types?
A: Cable fault refers to the cable in the preventive test insulation breakdown or in operation, due to insulation breakdown, conductor burnout, etc. and forced cable line blackout fault. Common faults are ground faults, short-circuit faults, disconnection faults, flashover faults and hybrid faults.
67, how to deal with single-phase ground faults in cable lines?
A: cable line single-phase ground faults in general, the cable conductor damage is only localized, if it belongs to the mechanical damage, and the soil near the point of failure is drier, you can generally carry out local repairs, add a false connector, that is, do not saw off the core of the cable, only to seal the fault point after insulation strengthening can be.
68, power cables should be laid before what tests and inspections?
A: Before laying the cable should be checked whether the type, specification and length meet the requirements, whether there is external damage, low-voltage cables with 1000V megohmmeter telemetry insulation resistance, resistance value is generally not less than 10MΩ, high-voltage cables with 2500V megohmmeter shaking resistance value is generally not less than 400MΩ.
69, the main plant laying cables in general should pay attention to what?
A: When laying cables in the main plant, attention should generally be paid to:
(1) Where the lead to the control room control cable should be laid overhead;
(2) 6KV cable should be laid in tunnels or rows of pipes, high water table can also be laid overhead or in rows of pipes;
(3) 380V cable when the two ends of the cable in zero meters is appropriate to use tunnels, ditches or rows of pipes, when one end of the equipment in the upper, one end in the lower, can be part of the aerial laying, when the water table is high, it is appropriate to overhead.
70, power cable shielding layer and outer shielding layer in what parts? What materials are used? What is the role?
A: In order to make the insulation layer and cable conductor has a better contact, eliminate the conductor surface of the conductor surface caused by the increase in electric field strength, generally in the conductor surface wrapped with metallized paper or semiconductor paper tape within the shielding layer. In order to make better contact between the insulation layer and the metal sheath, the outer screen layer is generally wrapped around the outer surface of the insulation layer. The outer screen layer and the inner screen layer of the same material, and sometimes external copper tape or braided copper wire tape.
71, briefly describe the composition and performance of epoxy resin compound.
A: epoxy resin compound from the epoxy resin to join the hardener, filler toughening agent and diluent composition. Has the following properties:
(1) sufficient mechanical strength;
(2) Excellent electrical properties;
(3) Stable electrical properties;
(4) Sufficient adhesion to non-ferrous metals;
(5) Good corrosion resistance;
(6) Resistant to rain, light, humidity and heat when used outdoors.
72, single-core cable sheath end of the grounding method in why must be installed along the cable parallel laying a return line?
A: In the metal sheath one end of the grounded cable line, in order to ensure that the induced voltage in the sheath does not exceed the permissible standards, must be installed along the cable line parallel laying of a conductor, and the conductor is grounded at both ends, this conductor is called the return line. When a single-phase ground fault occurs, the grounded short-circuit current can flow back through the return line to the center of the system, due to the return line through the ground current produced by the magnetic flux offset a portion of the cable conductor ground current produced by the magnetic flux, and thus reduce the short-circuit fault when the sheath of the induced voltage.
73, cable engineering can be divided into several projects?
A: (1) site transportation: including engineering materials from the warehouse to the construction point of loading and unloading, transportation and empty trucks back.
(2) Local engineering: including roadway excavation, tunnels, trench construction and so on.
(3) Laying works: including laying, intermediate head making, lifting cover, burying pipe, tide proofing, traction head making, etc.
(4) Both ends of the project: including support, suspension bridge and its foundation production and installation, terminal head production, oil pressure and signaling device installation, name kind of electrical performance testing.
(5) plug stop project: including oil-filled cable plug stop head production, oil supply tank, automatic drainage and signaling device installation.
(6) grounding project: including insulation joints, changeover box, protector, grounding box installation.
74, the acceptance of the cable line should be what checks?
A: (1) cable specifications should be in line with the provisions of the arrangement should be neat, no damage, complete, correct and clear labeling;
(2) The fixed bending radius of the cable, the relevant distance and the wiring of the metal sheath of single-core power cables should meet the requirements;
(3) Cable terminals, intermediate head without oil seepage and leakage, firmly installed, oil-filled cable oil pressure and meter setting value should meet the requirements;
(4) Good grounding;
(5) The cable terminals are of the correct phase color, and the metal parts of the brackets etc. are fully painted;
(6) Cable trench and tunnel, bridge should be free of debris, complete cover.
75, cable line positive sequence impedance measurement process what are the requirements?
A: The AC resistance of the cable conductor and the cable with the same inductive resistance of the three phase and known as the positive sequence impedance.
Positive sequence impedance of the cable line can generally be measured directly on the cable tray, the measurement of the general use of lower voltage, therefore, the need for step-down transformer step-down, step-down transformer using star wiring, capacity is generally more than 10kVA, a wider range of voltage regulation, the measurement of the AC power should be more stable to ensure that the measurement of the current to meet the requirements of the regulations, the actual voltmeter readings must be the cable end of the voltage, the test current is best close to the cable long-term voltage, the test current should be close to the cable long-term voltage, the test current should be close to the cable, the test current should be close to the cable long-term impedance. Voltage, the test current is best close to the cable long-term allowable current-carrying capacity, read the values of the meters, close the current and then read the values of the three tables at the same time.
- According to the Electricity Production Safety Regulations, what are the conditions that electrical workers must have?
A: Must have the following conditions:
(1) by a doctor’s appraisal of good health, no obstruction to work;
(2) have the necessary electrical knowledge, according to their duties and the nature of the work to master the relevant regulations, specialized techniques and safe operation techniques, and passed the examination;
(3) Skilled in first aid for electric shock.
77, cable in the transportation loading and unloading process should pay attention to what?
A: (1) in the transportation loading and unloading process, should not make the cable and cable tray damage, it is strictly prohibited to push the cable tray directly from the car, the cable should not be placed flat on the transportation, flat storage.
(2) Transportation or rolling cable tray before, must ensure that the cable tray is firm, cable winding tight, oil-filled cable to the pressure tank between the tubing should be fixed, no damage, the pressure tank should be firm, the pressure indication should meet the requirements.
78, what are the measures for cable fire protection?
A: (1) the use of flame retardant cables;
(2) The use of fire-resistant cable tray;
(3) the use of fireproof paint;
(4) cable tunnels, mezzanine outlets and other places to set fire partition walls, fire baffles;
(5) overhead cables should avoid oil pipelines, explosion-proof doors, otherwise there should be to take a local through the pipe or thermal insulation and fire prevention measures.
79, select the cross-section of power cables should be considered from which aspects?
A: The following aspects should be considered:
(1) cable long-term allowable operating current through;
(2) Thermal stability once the short circuit;
(3) The voltage drop on the line can not exceed the allowable operating range.
80, what are the advantages of power cables compared with overhead lines?
A: (1) reliable operation, due to installation in underground and other hidden places, small damage by external forces, less chance of failure, power supply safety, will not cause harm to the person;
(2) Small maintenance workload, no need for frequent inspections;
(3) No need to erect towers;
(4) Helps to improve power factor.